C2C3 random copolymer composition with improved balance between sealing initiation temperature and melting point

Patent metadata

Field	Value
Publication number	US-9932468-B2
Application number	US-201615551342-A
Country	US
Kind code	B2
Filing date	Feb 29, 2016
Priority date	Mar 2, 2015
Publication date	Apr 3, 2018
Grant date	Apr 3, 2018

Abstract

C 2 C 3 random copolymer composition with an improved balance between sealing initiation temperature (SIT) and melting point (Tm), i.e. low SIT and high melting point. In addition the inventive composition shows a broad sealing window, low hexane solubles and good optical properties, like low haze.

First claim

The invention claimed is:

1. A C 2 C 3 random copolymer composition comprising 3 polymer fractions (A), (B) and (C) with different comonomer content,
(A) 30 to 65 wt % of a C 2 C 3 random copolymer with a C 2 content (C 2 A) of 0.4 to 1.5 wt % based on copolymer (A) as measured with Fourier-transform infrared (FTIR) spectroscopy,
(B) 25 to 50 wt % of a C 2 C 3 random copolymer with a C 2 content (C 2 B) of 3.0 to 10.0 wt % based on copolymer (B) and
(C) 5 to 35 wt % of a C 2 C 3 random copolymer with a C 2 content (C 2 C) of 7.0 to 15.0 wt % based on copolymer (C),
whereby the sum of the amount of the 3 polymer fractions (A), (B) and (C) is 100% and
whereby the comonomer content of the polymer fractions increases from fraction (A) to fraction (C) according to (C 2 A)<(C 2 B)<(C 2 C),
and whereby the composition is characterized by
(i) a total C 2 content in the range of 3.0 wt % up to 7.0 wt %, as measured with Fourier-transform infrared (FTIR) spectroscopy,
(ii) a melt flow rate MFR2 (230° C.) measured according to ISO 1133 in the range of 2.0 to 15.0 g/10 min,
(iii) a melting temperature Tm as determined by DSC according to ISO 11357 of from 128° C. to 145° C.,
(iv) a crystallization temperature T c as determined as determined by DSC according to ISO 11357 of from 85° C. to 110° C. and
(v) a hexane solubles content determined in accordance with FDA section 177.1520 of at most 2.0 wt %.

2. The C 2 C 3 random copolymer composition according to claim 1 being further characterized by only one peak in the temperature range of 25 to −50° C. as determined by dynamic mechanical thermal analysis (DMTA) according to ISO 6721-7, indicating a single phase material and by three peaks in an analytical TREF (temperature rising elution fractionation)-measurement:
one in the temperature range of 0-40° C.,
the second one between 60 and 80° C., and
one peak between 80 and 100° C.

3. The C 2 C 3 random copolymer composition according to claim 1 , whereby the composition is obtained in the presence of a metallocene catalyst.

4. A process for producing a C 2 C 3 random copolymer composition according to claim 1 by a sequential polymerization process comprising at least two reactors connected in series, wherein the process comprises the steps of
a) polymerizing in a first reactor (R-1) being a slurry reactor (SR), propylene and ethylene, obtaining a C 2 C 3 random copolymer (A)
b) transferring said C 2 C 3 random copolymer (A) and unreacted comonomers of the first reactor in a second reactor (R-2) being a first gas phase reactor (GPR-1),
c) feeding to said second reactor (R-2) propylene and ethylene,
d) polymerizing in said second reactor (R-2) and in the presence of said first C 2 C 3 random copolymer (A) propylene and ethylene obtaining a C 2 C 3 random copolymer (B),
e) transferring said mixture of C 2 C 3 random copolymer (A) and C 2 C 3 random copolymer (B), and unreacted comonomers of the second reactor in a third reactor (R-3) being a second gas phase reactor (GPR-2),
c) feeding to said third reactor (R-3) propylene and ethylene,
d) polymerizing in said third reactor (R-3) and in the presence of the mixture of C 2 C 3 random copolymer (A) and C 2 C 3 random copolymer (B) propylene and ethylene obtaining a C 2 C 3 random copolymer (C),
said C 2 C 3 random copolymer (A), C 2 C 3 random copolymer (B) and said C 2 C 3 random copolymer (C) form the C 2 C 3 random copolymer composition according to claim 1 ,
whereby the polymerization takes place in the presence of single site solid particulate catalyst comprising (i) a complex of formula (I):

wherein
M is zirconium or hafnium;
each X is a sigma ligand;
L is a divalent bridge selected from —R′ 2 C—, —R′ 2 C—CR′ 2 —, —R′ 2 Si—, —R′ 2 Si—SiR′ 2 —, —R′ 2 Ge—, wherein each R′ is independently a hydrogen atom, C 1 -C 20 -hydrocarbyl, tri(C 1 -C 20 -alkyl)silyl, C 6 -C 20 -aryl, C 7 -C 20 -arylalkyl or C 7 -C 20 -alkylaryl;
R 2 and R 2 ′ are each independently a C 1 -C 20 hydrocarbyl radical optionally containing one or more heteroatoms from groups 14-16;
R 5′ is a C 1-20 hydrocarbyl group containing one or more heteroatoms from groups 14-16 optionally substituted by one or more halo atoms;
R 6 and R 6′ are each independently hydrogen or a C 1-20 hydrocarbyl group optionally containing one or more heteroatoms from groups 14-16;
R 7 is hydrogen or C 1-20 hydrocarbyl group optionally containing one or more heteroatoms from groups 14-16;
R 7 ′ is hydrogen;
Ar is independently an aryl or heteroaryl group having up to 20 carbon atoms optionally substituted by one or more groups R 1 ;
Ar′ is independently an aryl or heteroaryl group having up to 20 carbon atoms optionally substituted by one or more groups R 1 ;
each R 1 is a C 1-20 hydrocarbyl group or two R 1 groups on adjacent carbon atoms taken together can form a fused 5 or 6 membered non aromatic ring with the Ar group, said ring being itself optionally substituted with one or more groups R 4 ;
each R 4 is a C 1-20 hydrocarbyl group;
and (ii) a cocatalyst comprising a compound of a group 13 metal.

5. The process according to claim 4 , wherein the a catalyst comprises a complex of formula (III) or (III′)

wherein
M is zirconium or hafnium;
each X is a sigma ligand;
L is a divalent bridge selected from —R′ 2 C— or —R′ 2 Si— wherein each R′ is independently a hydrogen atom, C 1-20 alkyl or C 3-10 cycloalkyl;
R 6 is hydrogen or a C 1-10 alkyl group;
R 6′ is a C 1-10 alkyl group or C 6-10 aryl group;
R 7 is hydrogen, C 1-6 alkyl or OC 1-6 alkyl;
Z′ is O or S;
R 3′ is a C 1-10 alkyl group, or C 6-10 aryl group optionally substituted by one or more halo groups;
n is independently 0 to 4; and
each R 1 is independently a C 1-10 alkyl group.

6. A process for producing water or air quench blown films, comprising
i) blowing up a tube of a molten C 2 C 3 random copolymer composition according to claim 1 with air perpendicularly to the upwards direction from a side-fed blown film die;
ii) cooling the composition down with a water contact cooling ring or air quench; and
iii) folding and guiding the composition over deflector rolls onto a winder.

7. A sterilizable or sterilized article, comprising a C 2 C 3 random copolymer composition according to claim 1 .

8. A sterilizable or sterilized film comprising a C 2 C 3 random copolymer composition according to claim 1 .

9. The sterilizable or sterilized film according to claim 8 , whereby the films are characterized by
(i) a seal initiation temperature (SIT) of below 110° C.,
(ii) satisfying the equation T m -SIT≥25, wherein Tm is the melting point of the C 2 C 3 random copolymer composition,
(iii) a haze (determined according to ASTM D1003-00 on cast films with a thickness of 50 μm) of at most 2.5%,
(iv) a transparency (determined according to ASTM D1003-00 on cast films with a thickness of 50 μm) of at least 90.0%,
(v) a relative tear resistance in machine direction [N/mm] according to Elmendorf method (ISO 6383-2) for a cast film thickness of 50 μm of at least 28.0 N/mm and
(vi) a relative tear resistance in transverse direction [N/mm] according to Elmendorf method (ISO 6383-2) for a cast film thickness of 50 μm of at least 200.0 N/mm.

10. A film according to claim

Assignees

• Borealis Ag

Inventors

• Tranninger Cornelia
• Resconi Luigi
• Friedrich Karlheinz

Classifications

• C08L23/14 Primary

  Copolymers of propene (C08L23/16 takes precedence) · CPC title

• C08F2/001

  Multistage polymerisation processes characterised by a change in reactor conditions without deactivating the intermediate polymer (C08F295/00, C08F297/00 take precedence) · CPC title

• C08L23/16 Primary

  Ethylene-propylene or ethylene-propylene-diene copolymers · CPC title

• C08F210/06

  Propene · CPC title

• C08J5/18

  Manufacture of films or sheets · CPC title